Some underground storage tanks can corrode (i.e. bare steel) and poorly installed tanks may leak over time. When this occurs, the tank must be replaced or repaired. The removal and replacement of underground storage tanks are very expensive as this often requires the remediation of soil around the leaking tank. There are also instances, where for environmental or liability reasons, the tank owner may choose to upgrade tanks to secondarily contained tanks. Replacement is expensive.
Several suggestions have been made as how to retrofit or upgrade tanks using a secondary container or liner. For example, U.S. Pat. No. 5,261,764 to Walles, discloses installing at least one plastic coating within an existing tank to form a resultant double walled tank. Trussler, U.S. Pat. Nos. 5,060,817 and 5,102,005 provide external containment capsules which surround existing underground storage tanks. Jones, U.S. Pat. No. 3,167,209, teaches providing a flexible tank liner within an outer rigid tank. Other repairs methods include simply applying a coating of polyester or epoxy to the inside of a tank.
However, each of the methods has drawbacks for example, simply applying a coating of material on the inside of a tank produces a secondary tank or container which has little independent structural strength apart from the surrounding outer tank. In the event the outer tank corrodes or otherwise degrades sufficiently so that the outer tank cannot withstand the internal or external forces on the outer tank, it is desirable that the inner secondary tank have significant strength of its own. Further, providing a structurally sound inner tank allows for pressure monitoring of the annulus space created between the tanks using air or liquid as the annular space monitoring medium.
Placing a secondary containment vessel about the outside of an underground outer tank requires that all of the outer tank be exposed. This complete exposure of the tank from a covering layer of soil requires a great deal of work and expense.
The present invention has been developed to overcome the above cited deficiencies by providing a secondary or inner tank within a primary or outer tank. The secondary tank has significant self support or rigidity and requires a minimal amount of work to install within the outer tank.